Production of potassium nitrate



Patented Jan. 10, 1933 UNITED STATES OSCAR KASELITZ, F BERLIN, GERMANYrnonuo'rron or POTASSIUM NI'IR-ATE "No Drawing. Application filed June17, 1928, Serial N'o. 371,718,- and in Germany February 11, 1929.

My invention refers to the production of potassium nitrate, moreespecially by reacting on potassium chloride with nitric acid.

As is well known to those skilled in the art, difiiculties areencountered in this process in separating out the chlorine resultingfrom the; decomposition of the potassium chloride, without experiencinglosses in the valuable nitrogen oxides. The necessity of removing byevaporation the Water introduced together with the nitric acid involvesfurther economical losses.

I have now ascertained that these drawbacks can be avoided according tothe present invention, if to a solution rich in nitric acid potassiumchloride is added at ordinary or elevatedtemperature in such quantitythat at ordinary temperature only potassium nitrate separates out, whilethe solution is approximately saturated with potassium chloride. Theacid solution obtained in the reaction is then brought to the originalconcentration, adapted for the formation of potassium nitrate frompotassium chloride, by acting thereon with nitrous gases and air in anabsorption apparatus. During this operation only nitrosyl chlorideescapes, but no other chlorine compounds, nor elementary chlorine. Suchgases which may form during the formation of the potassium nitrate, moreespecially at an elevated temperature, namely hydrogen chloride and/orelementary chlorine, are added to the nitrous gases and thusreintroduced into the starting solution.

The nitrosyl chloride is now decomposed into nitrogen monoxide andchlorine. The chlorine is removed, while the nitrogen monoxide is addedto the nitrous gases, which may for instance result from the combustionof ammonia.

It may prove advantageous to first separate the nitrosyl chloride fromthe inert gases. I prefer using for this purpose absorbing media, suchas silica gel, active carbon or the like or ferric chloride. In thelatter case an addition compound FeCl NOCl is formed. In every case acomplete separation of the nitrosyl chloride from the valueless dilutinggases (mainly nitrogen) is obtained.

Theabsorbed nitrosyl chloride is set free by heating the absorbingmedium. It is then decomposed into-nitrogen monoxide and chlorine in asuitable manner, for instance by acting thereon with lime, iron orferrous chloride. The FeCl or CaCl formed in this reaction is removed,the nitrogen monoxide is quantitatively returned into the operation.

The heat required for expelling the nitrosyl chloride from the absorbingmedia and for splitting oif the nitrogen monoxide may be furnished bythe hot nitrous gases resulting from the combustion of ammonia. Heattransmission may be effected directly or indirectly. I prefer leadingfor instance the two nitrous gases or part of them first over theabsorbing medium saturated with nitrosyl chloride and thereafter overcaustic lime which is thus heated to thetemperature required for thedecomposition of the nitrosyl chloride.

Ermmple 49' kilograms of a solution containing 46.5% HNO 16.5% KNO andO.!l% KCl are stirred with kilograms potassium chloride. After coolingdown the solution contains 31.5% HNO and 3.5% I-IGl, while kilogramspotassium nitrate separate out. The liquid separated from the potassiumnitrate is now treated in an absorption apparatus with nitrous gases andair, until all the chlorine has escaped in the form of nitrosylchloride, whereby a solution having the composition of the solutionoriginally used is obtained. 1.3cubic metres NO- are required in thisoperation and there escapes a mixture of 1.2 cubic metres NOCl and air.

In practising this process I may for instance introduce the nitrousgases already during the reaction between potassium chloride andnitric'acid, so that the concentration of' HNO in the reaction solutionremains substantially constant and the reaction is greatly expedited.

I may also operate in a continuous manner, to the reaction solutionfresh potassium chloride being continuously added, and the nitric acidbeing permanently maintained a at the concentration required for a fastreaction by simultaneously introducing nitrous gases and air, thepotassium nitrate formed being removed at the same time.

The novel process involves a number of great advantages as compared withsimilar processes hitherto suggested. The introduction of water isavoided altogether, merely nitrous gases and potassium chloride beingintroduced, and it is therefore unnecessary to remove water byevaporation or to remove any solution. F or this reason all losses ofnitrogen and potassium are avoided also.

The losses of valuable nitrogen oxides re sulting by imperfectabsorption, when producing nitric acid, are avoided also, the absorptionof the nitrosyl chloride occurring in a practically quantitative manner.

The potassium nitrate obtained according to this process issubstantially free from chlorine. The acid solution adhering to the saltcan easily be removed by filtering or centrifuging, followed by washing.It is, however, also possible to neutralize the adhering solution withpotassium carbonate or ammonia, whereby a neutral potassium nitrate isobtained in a simple manner. This latter mode of proceeding involves thefurther advantage that part of the water is removed, which can then bereplaced by the dilute nitric acid which is obtained by cooling thenitrous gases resulting in the combustion of ammonia.

Various changes may be made in the details disclosed in the foregoingspecification without departing from the invention or sacrificing theadvantages thereof.

In the claims affixed to this specification no selection of anyparticular modification of the invention is intended to the exclusion ofother modifications thereof and the right to subsequently make claim toany modification not covered by these claims is expressly reserved.

1. The method of producing potassium nitrate comprising acting onpotassium chloride with a solution of nitric acid separating thepotassium nitrate formed, treating the acid solution remaining overafter separation of potassium nitrate with nitrous gases and air inorder to freshly form nitric acid and removing chlorine in the form ofnitrosyl chloride substantially free from other chlorine compounds andfrom elementary chlorine, decomposing the nitrosyl chloride and addingthe nitrogen oxide resulting in this decomposition to the nitrous gases.

2. The method of producing potassium nitrate comprising acting onpotassium chloride with a solution of nitric acid, separating thepotassium nitrate formed, treating the acid solution remaining overafter separation of potassium nitrate with nitrous gases and air inorder to freshly form nitric acid and removing chlorine in the form ofnitrosyl chloride substantially free from other chlorine compounds andfrom elementary chlorine, separating the nitrosyl chloride from theinert gases by adsorption, decomposing the nitrosyl chloride and addingthe nitrogen oxide resulting in this decomposition to the nitrous gases.

3. The method of producing potassium nitrate, comprising acting onpotassium chloride with a solution of nitric acid by introducing nitrousases and air into said solution in order to f i'eshly form nitric acidtherein and removing chlorine therefrom in the form of nitrosyl chloridesubstantially free from other chlorine compounds and from elementarychlorine, decomposing the nitrosyl chloride and adding to the nitrousgases the nitrogen oxide resulting in this decomposition.

4. The method of producing potassium nitrate comprising continuouslyadding to a solution of nitric acid potassium chloride and a gas mixturecontaining nitrous gases and air to continuously form potassium nitrate,removing the same, and nitrosyl chloride, substantially free from otherchlorine compounds and from elementary chlorine, decomposing thenitrosyl chloride and adding to the nitrous gases the nitrogen oxideresulting in this decomposition.

The method of producing potassium nitrate comprising continuously addingto a solution of nitric acid potassium chloride and a gas mixturecontaining nitrous gases and air to continuously form potassium nitrate,removing the same, and nitrosyl chloride substantially free from otherchlorine compounds and from elementary chlorine, decomposing thenitrosyl chloride and adding to the nitrous gases the nitrogen oxideresult ing in this decomposition, the relative amounts of potassiumchloride, nitrous gases and air being controlled to maintain asubstantially constant concentration of the nitric acid solution.

In testimony whereof I afiix my signature.

OSCAR KASELITZ.

